(CNN) -- Voters in Guinea cast ballots Sunday in the first free election since the west African nation gained independence in 1958.

"With successful elections, a democracy will be born, and all Guineans together will have together taken a giant step forward," the U.S. ambassador to the country, Patricia Newton Moller, said in a message to the country ahead of the first round of voting.

The country has been ruled by a series of authoritarian and military dictators since it gained independence from France, its former colonial master.

The most recent coup came in December 2008, the day after the death of longtime President Lansana Conte, who had himself seized power in 1984.

Capt. Moussa Dadis Camara led the 2008 coup and promised elections and the introduction of civilian rule, but by the following summer it seemed clear that he planned to run for president himself, according to the U.S. State Department.

The opposition organized a protest against him in a stadium in the capital Conakry in September 2009, but the military attacked the demonstrators.

At least 150 people were killed, more than 100 were raped, and at least 1,000 were injured, according to the U.S. government and international human rights groups.

At least 100 bodies were never found, Human Rights Watch charges.

Camara was seriously wounded in an assassination attempt by an aide in December 2009, and flown abroad for medical treatment.

He survived, but agreed not to return to the country.

Minister of Defense Brig. Gen. Sekouba Konate became interim president, paving the way to the elections on Sunday.

Twenty-four candidates are running for president, including four former prime ministers, according to Human Rights Watch, which has been cautiously optimistic about the vote.

"The Defense Ministry's promise to keep the military in barracks during the election period, and to back whoever wins is a very positive sign," Human Rights Watch said Friday.

"A successful, credible election could finally end over 50 years of authoritarian and abusive rule," the activist group said.

"The new president and government will have their work cut out for them," HRW's Corinne Dufka said. "They should waste no time addressing the deep-rooted causes of years of crisis -- endemic corruption, impunity, crushing poverty, and the inequitable distribution of natural resource wealth."

The country's electoral officials, cell phone companies and U.S. embassy have worked together to set up a system where voters can send text messages if they see voter fraud or intimidation, said Moller, the U.S. ambassador.

Guinea, a country of about 10 million people, has rich reserves of bauxite, an important aluminum ore -- possibly as much as half the world's reserves, according to the State Department.

It also has gold and diamond mines, and grows rice, coffee, bananas, pineapples and palm products.